Glass surfacing method and apparatus



Oct, 1, 1946.- G. B. WATKINS ETAL 2,408,496

.GLASS SURFACING METHOD AND APPARATUS Filed July 25, 1941 zsheets-sheet. 1

V inventor:

I Oct. 1,1946. e. B. WATKINS ETAL- 9 GLASS SURFACING METHOD ANDAPPARATUS,

il dudl 25, 1941 2 Sheets-Sheet 2 :12 J, l" I I ll:

Q i: x z N l Z I I 'I l Z5 Z I g Imnentors attorney Patented Oct. 1 1946 GLASS SURFACING ME'rnon ANi APPARATUS,

George B. Watkins, Toledo, Ohio, and Conrad'B. Schafer, Charleston, W.Va; assignors to Libbey-Owens-Ford Glass Company, Toledo; Ohio.

.a corporation of Ohio Application July .23, 1941, SerialNo. 403,634 2Claims (01. 51 2ss) The present invention relates broadly to thesurfacing (grinding and polishing) of glass and more particularly toanimproved method of and apparatus for surfacing relatively small platesof -glass.

Generally stated, this invention is primarily concerned with themanufacture of prismatic rear view mirrors for automotive vehicles andthe like of the type comprising a plate of glass of substantiallytriangular shape in cross section having one side thereof plane andperpendicular with respect to the upper and lower edges of the plate andthe other side' arranged at a slight angle with respect to the planeside. The plane side of the glass plate is provided with a suitablereflecting media such as a silver coat. It has been found that such amirror is very effective in reducing glare and therefore makes asatisfactory rear view mirror for automotive vehicles and the like.

An important object of the invention is the provision of a novel methodof and apparatus for surfacing (grinding and polishing) relatively smallplates of glass to render them of substantially triangular shape incross section and suitable for use in the manufacture of prismaticmirrors of the above character.

Another important object of the invention is the provision of such amethod and apparatus whereby a relatively largenumber of glass'platescan be simultaneously ground and polished in a single grinding andpolishing operation rapidly, accurately and economically.

A furtherimportant object of the invention is theprovision of such amethod and apparatus wherein the glass plates are supported in such amanner that they will be securely held against displacement during thesurfacing operations and alsoin which first the grinding and then thepolishing of the plates may be accomplished without disturbing therelative positions thereof.

Other objects and advantages of the invention willbecome more apparentduring the course of the following description, when taken in connectionwith the accompanying drawings.

In the drawings, wherein like numerals are employed to designate likeparts throughout the same:

Figs. 1, la and 1b are diagrammatic plan views illustrating respectivelyan assembly table, a grinding machine and a polishing machine on whichthe assembling of the glass plates and the subsequent grinding andpolishing thereof may be accomplished;

Fig. 2 is a plan view of the removable top for supporting the glassplates'during grinding and p li h n i Fig. 3 is a side elevation,partially in section, of a grinding or polishing machine showing theremovable top associated therewith;

Fig. 4- is'an enlarged sectional view showing the manner in which theremovable top is held upon the machine;-

Fig. 5 is a detail sectional view showing the manner in which the glassplates are secured upon the removable top;

7 Fig. 6is asimilar view showing the glass plates after being groundandpolished;

Fig. '7 is a transverse section of a mirror formed from one of the glassplates; and

Fig. 8 is a detail sectional Y iew of a modified form of removable top.I

With reference now to the drawings, there is shown in Fig. 7 a prismaticrear view mirror for automotive vehicles comprising a glass plate Ill inthe formof a triangular prismoid having a plane back surface llextending perpendicular with respect to the upper and lower edges 52 andI8 thereof and a front surface I 4 which is arranged at a'slightanglewith respect to the back surface H. .The back surface it isprovided with any suitable type of reflecting media, such as a silvercoat l 5, covered by the usual protective backing I6 if desired.

In Figs. 1 to 6 inclusive is illustrated a preferred form of apparatusfor surfacing a plurality of glass blanks to produce the triangularmirror plates It The forming of the mirror plates is accomplished inthree principal operations consisting of (l) properly mounting the glassblanks from which the mirror plates are to be made; (2) grinding theblanks to form mirror plates of the desiredtriangular shape in crosssection; and (3) polishing the ground surfaces of the mirror plates.

The mounting of the glass blanks may be carried out upon any suitabletableor the like I? (Fig. 1), after which they are transferred to thegrinding machine is (Fig. la) and acted upon by the grinding runner isrotatably carried at the lower end of a vertical shaft .20. After beingground, the mirror plates are transferred to the polishing machine 2 i(Fig. 12)) upon which thegroundsuriaces are polished by the freelyrotatable polishing runners 22 carried by a frame 23 mounted upon avertical shaft 24.

The grinding and polishing machines I8 and H may be of the constructionillustrated in Fig. 3 comprising a, supporting housing 25 providedtherein with the spaced upper and lower bearings 26 and 21 in which isjournaled a vertical shaft 28 having keyed thereto a worm gear 29.Meshing with the worm gear 29 is a worm 3O keyed to a drive shaft 3|driven from a suitable motor.

Keyed to the upper end of the vertical shaft 28 of the grinding orpolishing machine is a circular supporting plate 32 upon which issupported the removable top 33 carrying the glass blank 34 to besurfaced (Fig. The removable top 33 consists of a relatively large metaldisk provided upon its upper surface with a plurality of spaced,parallel ribs 35 defining therebetween the relatively long, narrowrecesses 35. That is to say, the ribs 35 constitute the opposite sidewalls of the recesses, while the outer ends of the said.

recesses may be closed by a vertical rib 31 extending around theperimeter of the top 33. Also, if desired, the longer recesses 33 can bedivided intermediate their ends by a vertical rib 38 arranged at rightangles to the ribs 35.

The bottom 33 of each recess 36 inclines downwardly from one rib 35 toan adjacent rib 35, with the angle of inclination thereof correspondingto the angle of the front surface IA of the mirror plate It. Althoughnot essential, it is preferred that the bottom 39 of adjacent recesses38 incline downwardly in opposite directions as shown in Fig. 4.

The glass blanks 34 consist of relatively long, narrow strips of glassand, as illustrated in Fig. 5, these blanks are rectangular in crosssection, having their opposite surfaces plane and parallel with oneanother. Consequently, when the blanks are placed within the recesses 36in th table top they are disposed in an inclined position. When mountingthe glass blanks 34 within the recesses 36, a relatively thin layer ofsuitable plaster, such as plaster of Paris or the like 49, is firstplaced within the bottom of each recess and the glass blank laidthereupon with the bottom surface of the glass blank being parallel withthe bottom of the respective recess. Additional plaster 4! may then bespread over the upper surface of the glass blanks to completely coverthe same and to also completely fill in the spaces between adjacentblanks, the said blanks being firmly held in place upon setting of theplaster.

The mounting of the glass blanks 34 upon the table top 33 may beaccomplished while said table top is supported upon a suitable assemblytable as indicated at I? in Fig. 1, after which the top, with the glassblanks, is transferred to the grinding machine l8. To facilitate thehandling of the top, it may be provided at diametrically opposlte pointswith handles 42 and 43. Also, to facilitate the positioning of the topupon the grinding machine, the supporting plate 32 of the machine isprovided at diametrically opposite points with vertical dowels 44 and 45which are received within recesses 46 formed in the under side of thetop. To further assist in securing the removable top 33 upon thesupporting plate 32, the vertical shaft 28 of the machine may beprovided at its upper end with a reduced cylindrical extension 41received within a recess in the under surface of said removable top.

Upon grinding of the glass blanks 34, the inclined upper surfacesthereof will be gradually ground away until said surfaces are flat anddisposed in a common horizontal plane, as shown in 4 Fig. 6. This willresult in th upper surface of each glass blank being at a slight angleto the bottom surface thereof so that the upper surface will constitutethe front surface M of the mirror plate In and the bottom surface theplane back surface ll of said mirror plate which is perpendicular withrespect to the upper and lower edges l2 and I3.

After the glass blanks have been properly ground, the removable top 33is transferred from the grinding machine [8 to the polishing machine 2!and the upper surfaces thereof smoothed and V polished. After polishing,the glass blanks are removed from the recesses 36 in the top 33 andfinished, after which the plates are properly washed and cleaned and thereflecting media I5 to protective backing if: then applied and the planesurface H to form the completed mirror shown in Fig. '7.

In Fig. 8 is illustrated a modified form of removable top 33in which theribs 49 corresponding to th ribs 35 are removable. The ribs 49 consistof separate strips seated within grooves 59 in the upper surface of thetop 33 and removably secured therein by screws 5|. If desired, the rib31 extending around the perimeter of the top 33 may also be maderemovable to facilitate handling of the glass plates.

It is to be understood that the form of the invention herewith shown-anddescribed is to be taken as the preferred'e'mbodiment of the same, andthat various changes in the shape, size and arrangement of parts may beresorted to without departing from the spirit of theinvention or thescope'of the subjoined claims.

We claim:

l. The method of forming mirror plates substantially triangular in crosssection, comprising supporting a, plurality of glass blanks which aresubstantially rectangular in cross section in a horizontally inclinedposition, coverin said blanks with a bedding material to fill the spacesbetween adjacent blanks and to provide a flat unbroken surfacethereabove, and then simultaneously grinding away the bedding materialand the upper inclined surfaces of the glass blanks until said uppersurfaces are in a common horizontal planeand at an angle'with respect tothe bottom surfaces thereof.

2. The method of forming mirror plates substantially triangular in crosssection, comprising supporting a plurality of glass blanks which aresubstantially rectangular in cross section in a horizontally inclinedposition, covering said blank with a bedding material to fill the spacesbetween adjacent blanks and to provide a flat imbroken surfacethereabove, then simultaneously grinding away the bedding material andthe upper inclined surfaces of the glass blanks until said uppersurfaces are in a common horizontal plane and at an angle with respectto the bottom surfaces thereof, and then polishing said ground surfaceswithout changing the relative positions of the glass blanks.

GEORGE B. WATKINS.

CONRAD B. SCHAFER.

